@mixin position(){
    position: absolute;left: 0;right: 0;top: 0;bottom: 0;margin: auto;
}
@mixin warp($width:100%,$height:auto,$top:0,$bottom:0,$hidden:hidden){
    width: $width;height: $height;margin: $top auto $bottom;overflow: $hidden;
}
@mixin width($width:100%,$height:100%){
    width: $width;height: $height;
}
@mixin center($size:12px,$color:#fff,$lineheight:20px,$center:center,$bold:400){
    font-size: $size;color: $color;line-height: $lineheight;text-align: $center;
    font-weight: $bold;
}
@mixin background($url:0,$no:no-repeat,$center1:center,$center2:center,$cover:cover){
    background: url($url) $no $center1 $center2/$cover;
}



